The advent of metal and metal alloy containers for beverages, food and other goods led to the development of a variety of means for closing and sealing such containers. Many such closures include permanently affixed container ends which are cut away with separate hand tools. This type of closure is in common use with cans for holding a variety of food products, which are typically stored in a kitchen area and suitable hand tools for opening the container are thus readily accessible.
Beverage containers, on the other hand, have more commonly been developed with convenient, integrally attached tabs that are torn away to form an opening in the container. Many containers of non-carbonated beverages, such as fruit juice and the like, have an opening in an end wall that is closed by a strip of removable tape. This type of closure is not entirely satisfactory, however, because of the less sturdy nature of such closures, and the susceptibility of them to tampering.
Carbonated beverages generally require more secure closures, and have evolved with a variety of so-called "pop-top" or "pull-tab" devices for forming an opening in an end wall of the container. Early devices included removable sections joined to the container end along a frangible score line, and a pull tab or ring attached to the removable section so that it could be pulled from the container end, separating along the score line, to form an opening. The removed section and the attached pull tab or ring were then discarded. This approach was unsatisfactory because of the ecological damage created by the discarded tabs.
To alleviate the environmental harm produced by such removable pull tabs, closures were developed that remained attached to the container after being opened. These closures also comprise a frangible section of the container end wall, joined to the end wall along a score line, and including an actuating ring associated with the frangible section. However, rather than being completely removed from the container end wall and discarded, the frangible section remains attached to or captive on the container. The most commonly used closure of this type is pushed into the container by the actuating ring. While this solves the problem related to environmental damage that was caused by discarded pull tabs, it gives rise to new problems. For instance, the container end wall, including the frangible section, sometimes become contaminated with dirt or other foreign material. Consequently, when the section is displaced into the interior of the container to form an opening, the contents of the container are subject to contamination by the inwardly displaced, contaminated frangible section.
To solve the latter problem, some containers are provided with frangible sections that are separated along a score line from an end wall of the container to form an opening, but instead of being pushed into the container, are folded back externally of the container. In some constructions, this type of closure remains attached to the container, and in other constructions the closure is completely separated from the container. These types of opening forming means are commonly used on pet food containers, or containers of solid food products, or other materials, and while they solve the problems related to contamination of the contents of the container, they raise the possibility of injury to a person handling the container because of the exposed sharp edge of the separated section. Efforts have been made to solve this problem in some prior art devices by placing folds in the material of the end wall adjacent the severed edge, or by providing a layer of protective material over the severed edge. Such prior art devices are either difficult and expensive to produce, or are not entirely satisfactory in operation.
Accordingly, there is need for a simple and inexpensive closure means for containers, especially of the tear tab variety, which is captive on the container and thereby does not lead to environmental contamination by discarded tabs and removable sections, but which also does not enter the container and potentially contaminate the contents of the container, or expose sharp edges which may injure the user.